Excitonic coherence in a confined lattice : a simple model to highlight the relevance of the perturbation theory

Vincent J.C. Pouthier (1)

1 UTINAM - Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213)

The exciton-phonon system in a confined environment is revisited within standard perturbation theory. Special attention is paid for describing the time evolution of the excitonic coherences at finite temperature. To proceed, the system involving an exciton dressed by a single phonon mode is considered. Due to its simplicity, it is solved exactly so that the relevance of the perturbation theory is checked. Within the nonadiabatic weak coupling limit, it is shown that several time scales govern the coherence dynamics. In the short time limit, the coherences behave as if the exciton was insensitive to the phonon bath. Then, quantum decoherence takes place. Finally the coherences recur almost periodically at specific revival times. Coherence decay and revival strongly depend on the nature of the excitonic states. In particular, for odd lattice sizes, the coherence of the state exactly located at the band center survives over a very long time scale. Therefore, confinement-induced decoherence softening favors high fidelity quantum state transfer and allows to encode the information on a quantum bit almost insensitive to quantum decoherence.

Mots clés: decoherence; open systems; quantum statistical methods; excitons; phonons; decoherence

Domaines: Autre [cond-mat.other]; Physique Quantique [quant-ph]

Vincent J.C. Pouthier. Excitonic coherence in a confined lattice : a simple model to highlight the relevance of the perturbation theory. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2010, 83 (8), pp.085418. ⟨10.1103/PhysRevB.83.085418⟩. ⟨hal-00569931⟩